8 x 13 x 4 Sealed Ball Bearing One Bearing 8 x 13 x 4 metal shielded, radial and deep groove ball bearing, 8 x 13 x 4 bearing is made of stainless Steel with stainless Steel balls and steel cage,8 x 13 x 4 bearing is closed with metal shields to protect the bearing from dust or any possible contamination,8 x 13 x 4 bearing is shielded and self lubricated,the quality is set to EMQ (electric motor quality) to ensure high speed,8 x 13 x 4 bearing is lubricated with grease.